For people with cardiovascular disease and those who are at high risk for clots in the legs, a single injection of the blood thinner heparin did the trick, according to research presented today at the American Heart Association’s Scientific Sessions 2001 conference. People with a history of heart disease or stroke are considered at high risk for deep-vein thrombosis (DVT) on long plane rides, says researcher Gianni Belcaro, Ph.D., from the University of Chieti in Chieti, Italy. However, DVT is a condition that can also affect people who are apparently healthy, he says.
Deep-vein thrombosis is a potentially life-threatening disorder in which blood clots form in the deep veins in the body, particularly the legs. Approximately 4 percent to 5 percent of high-risk individuals may suffer DVT on flights of 10 hours or more, he says. “If you sit for hours on a plane, you may get a clot in a vein,” says Belcaro. “Immobility is the cause, but low pressure in the cabin, low humidity and dehydration may also contribute.”
This research, conducted by an international group of researchers from the UK, Australia and Italy and led by Belcaro and Andrew Nicolaides, M.D., from the University of Chieti and St. Mary’s and Ealing Hospitals in London, was triggered by recent concerns about the risk of another complication called venous thromboembolism, where clots in the veins may travel to the lungs after long-haul flights. However, no evaluation had been performed to determine a solid connection between DVT and thromboembolism. Now three studies have been completed.
The LONFLIT 1 study evaluated the occurrence of DVT as a consequence of long-haul flights. In the study, 355 subjects at low risk of DVT and 389 high-risk subjects were recruited. The average age of subjects was 46 years, and 56 percent were male. Low-risk subjects had no cardiovascular disease and were not taking any prescription medication. The high-risk profile included previous incidences of thrombosis, blood-clotting problems and circulatory problems in the legs. All subjects flew economy class, and the average flight duration was 12.4 hours.
Participants underwent ultrasound scans within 24 hours before and after the flights to determine if DVT had occurred. In low-risk subjects, no DVT was found. However, in high-risk subjects, 19 subjects had thromboses with 13 having DVT and six with superficial thromboses (clots not involving a deep vein).
LONFLIT 2 evaluated whether compression stockings could effectively prevent or minimize DVT. Researchers recruited 833 subjects, 57 percent of whom were male, with an average age of 44.8 years. They were randomized into a control group of 422 people and a “stocking” group of 411, who wore below-the-knee stockings. Again the average flight duration was 12.4 hours, and ultrasound scans were made before and after the flights. In the control group, 4.5 percent of subjects developed DVT, while only .24 percent of subjects wearing stockings developed DVT.
The difference was significant, says Belcaro. The incidence of DVT observed when subjects were wearing stockings was 18.75 times lower than in controls.
Finally, LONFLIT 3 evaluated how well aspirin and heparin prevent DVT in high-risk individuals.
Heparin prevents clotting, and is used to prevent unwanted clots in surgical patients. Aspirin prevents platelets from sticking together. For the third LONFLIT, 300 high-risk subjects were randomized into three groups: a control group, an aspirin group who took 400 milligrams in one dose a day for three days starting 12 hours before their flights, and a low-molecular-weight heparin group who received the drug in a single weight-adjusted dose injected two to four hours before their flights. Completing the study were 249 subjects, 65 percent of whom were male, with an average age of 47. Age, gender, and risk factors were still comparable among the groups.
Of the 82 people completing the study in the control group, 4.8 percent developed DVT and two people developed superficial thromboses. Of the 84 subjects in the aspirin group, 3.6 percent developed DVT and two people developed superficial thromboses. In addition, mild side effects were observed in 13 percent of the aspirin subjects. Of the 82 subjects in the heparin group, no cases of DVT and only one superficial thrombosis were recorded.
“These findings suggest that DVT prevention with stockings is useful for low- to medium-risk patients and a single dose of heparin for high-risk subjects,” says Belcaro. “The heparin can be given in small doses injected into the subcutaneous tissue. It’s easy, and it should be prescribed for high-risk patients.” Belcaro says further studies are under way.
Co-authors are: Marco Bucci, M.D.; George Geroulakos, M.D.; Kennet A. Myers, M.D.; Michelle Winford, M.D.; Maria Rosaria Cesarone, M.D.; Maria Teresa De Sancris, M.D.; Lucrezia Incandela, M.D.; and Andrew N. Nicolaides, M.D.
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Abstracts 2497 & 3853
NR01 – 1363 (SS01/Belcaro)